Bridge deck

ABSTRACT

An arrangement in a bridge deck and the like surface-forming structure to be subjected to mobile concentrated loads of small extent, so-called point loads, moving along the bridge deck, comprises a plurality of neighboring elongate units, so-called deck slabs (1), supported by and anchored to a base in the form of beams or like supporting system (25), the units or slabs (1) being provided with a tongue (8) and groove (9) adapted to laterally join neighboring units. The groove (9) and tongue (8) are located in such manner relative to the unit or slab portions engaging with the base that when the units are positioned on the base (25), at least portions of a first edge part of each unit are directly supported by and anchored to the base, while, by the groove/tongue engagement, an opposite second edge part is supported by the first edge of the neighboring unit, which is directly supported by the base.

BACKGROUND OF THE INVENTION

The present invention relates to a bridge deck of the type used tosupport mobile concentrated loads, as for example, in roadway systems.

Most bridges, particularly beam bridges, comprise a bridge decksupported by underlying beams. Frequently, this bridge deck is aconcrete deck resting on longitudinal and, in some cases, transversebeams. A conventional concrete bridge deck is exceedingly heavy--theweight per m², including the asphalf wearing surface, amounts roughly to700 kg--and is manufactured in a time-consuming manner. In the past fewyears, a great many bridges were found to be severely damaged, mainly bywinter-time salting, and in need of reconstruction. Reconstruction of abridge with a concrete deck means that the bridge must be closed, whollyor partly, for a very long period. Light bridges are sometimes providedwith a deck of planking which in its entirety can be supported bysecondary beams or the like. Wooden decks have a relatively short lifeand must be reconstructed time and again.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a completely new typeof bridge deck which is very light and is easily laid in both newconstructions and reconstructions and when reconditioning, and which hasa life far exceeding that of currently available bridge decks. A furtherobject is to provide a bridge deck surfacing having a life which is manytimes longer than that of the present-day surfacings.

The characteristic features of the new bridge deck are stated in theappended claims.

The inventive bridge deck is preferably made by extrusion of aluminum orlike light-alloy metal, whereby it is possible, in a practical manner,to obtain units with insignificant tolerance variations and considerabletorsional strength.

To date, light metal, in particular aluminium, has been used but to alimited extent in bridge constructions, and one of the main reasons isthat aluminium meets with fatigue failure more easily than e.g. steel,when subjected to pulsating loads. Especially in a bridge deck, thetransverse units are subjected one after the other to the load of apassing vehicle, and this causes the units to move relative to oneanother, no matter how firmly they are affixed to the supporting base.The critical points thus are the joints between the units, whereconsiderable stress occurs when a load leaves one unit and moves to thenext. Previous attempts at solving this problem by means of tongue andgroove arrangements have been unsuccessful.

The invention is based on the insight that the units or bridge deckslabs must be arranged such that any relative movement in the jointsbetween the slabs is eliminated, and this constitutes an essentialfeature of the invention.

According to the invention, the units or slabs forming the bridge deckare in fact designed such that one side of each slab is rigidlysupported by underlying beams or the like, whereas the opposite side issupported by the rigidly supported side of the neighboring unit. This isachieved in that the bridge deck slabs are provided with a special typeof tongue and groove and are anchored to a load-bearing structure so asto guarantee the engagement between the tongue and groove. To achievesuch anchoring which is to prevent any play between the bridge deckslabs and the structural beams, the point of engagement of the bridgedeck slabs and also the attachment member must be designed in a specialmanner. To this end, a projecting of the bridge deck slab is providedwith an upwardly open channel with which a complementarily designedportion of an attachment member attachable by leverage, as by means of ascrew, is adapted to engage so as to press the lower side-edge of theslab against the base with great force.

To guarantee the engagement of the tongue and groove arrangement, theslabs must be pulled closely together in transverse direction. Duringextrusion, the material may be bent to a certain extent, and this mustbe accommodated during mounting. To this end, the attachment member isprovided with a noncircular hole which allows adjustment after initialtightening of the screw joint in that the shank of the screw is used asan abutment for a wedge member inserted between the shank and the edgeof the slab. When the correct position has been reached, the screw jointis tightened permanently.

Bridge decks are usually provided with a surfacing which, for the bridgedeck according to the invention, is a special type of coating. Tofacilitate the use of a particularly thin coating, the bridge deck slabsare slightly bevelled along their upper abutting edges.

The coating of the bridge deck according to the invention is made up ofa layer of primer applied directly to tha aluminium surface, a layer ofpermanently elastic plastic material, acrylic plastic or the like havinga thickness of about 1-2 mm and, upon this, a layer of substantiallyrigid, i.e. somewhat flexible, plastic material, acrylic plastic or thelike bonded to said permanently elastic material and having a thicknessof about 3-10 mm and, finally, a hardwearing granulated mineralinterspersed in the rigid material before this has set so that thegranulated material will be firmly bonded therein.

When a vehicle is passing, bending motions arise in the coating and alsoin the deck slabs. These motions are absorbed in the permanently elasticlayer, but in order to eliminate the risk that any changes in theangular relationship between the joints to the units become so greatthat the rigid layer fractures, the above-mentioned bevelling isprovided which gives a deeper layer of permanently elastic materialprecisely at the joints, which can yield and allow deformation by alarger radius than the rigid material without breaking. The coatinglayer as described is completely tight and protects the underlyingbridge deck effectively from water, salt and the like. Even if the rigidsurface layer should be damaged, for example during snow clearing, orowing to an excessive change in the angular relationship between thejoints, the permanently elastic layer adhering to the bridge deck andserving as a sealing compound ensures that no water can leak in.

Even though the inventive bridge deck is very strong, there may besituations when one or more bridge slabs must be replaced. The describedstructure with the tongue and groove portions which have a close fit andare positioned close to the upper surface of the bridge deck, renders itpossible to tilt one or more bridge slabs in a simple manner, after theattachments have been loosened, and then to replace them by new slabs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail below, reference beinghad to the accompanying drawing in which:

FIG. 1 is a cross-sectional view of a bridge deck slab for use in thebridge deck according to the invention;

FIGS. 2 and 3 are cross-sectional views of end sections for connectingwith the bridge deck slabs;

FIGS. 4, 5 and 6 illustrate an attachment member for attaching thebridge deck slabs and the end sections to the structural beams, as seenfrom above, from below and from one end, respectively; and FIG. 7 is across-sectional view of a portion of a mounted bridge deck and itscoating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The bridge deck slab 1 shown in FIG. 1 comprises an upper wall 2, alower wall 3, side walls 4 and 5 and internal brace walls 7. "Junctions"are formed by material thickenings where the walls converge. Each ofside walls 4 and 5 includes a portion which is substantiallyperpendicular to the upper wall, and there one side wall is providedwith a tongue 8 having a rounded outer edge, and the other with a groove9 with rounded extremities and a rounded bottom. The joint between theupper wall and the side walls is bevelled, as shown at 10 and 11.

The side walls 4 and 5, which have their thickest portions adjacent theupper wall and are inwardly inclined below the perpendicular portionsand tapering, converge with the bottom wall 3 and respective brace wallsto respective lower junctions. From these junctions there project; flushwith the lower wall strips 12 and 13, respectively, which are providedwith channels or grooves 14 and 15, respectively, having a roundedbottoms adjacent the respective side walls.

The height of the bridge deck slab at its opposite sides as counted fromthe somewhat thickened edges at the bottom wall to the center of thetongue 8 and groove 9, i.e. the heights designated a and b,respectively, differs. One height is slightly lower, the differencebeing between 0.1 and 0.4 mm. It is per se possible to choose whichheight is to be the lower one; the only condition is that all slabs in aseries are made in the same manner. In the embodiment preferred, theheight b of the side having the tongue is lower than the height of thegrooved side (a). This means that when two slabs lie close together on abeam, the tongue 8 will be positioned somewhat lower than the groove 9,and when the slabs are pressed together, the bottom edge at the tongueside will be slightly raised from the beam surface. When the slabs havebeen fixed in the manner described below, stresses acting on the "tongueside" of one slab will be transferred via the tongue and groove to thegrooved side of the neighboring slab and, via the side wall 5 thereof,to the supporting beam. Consequently, a row of bridge deck slabs mountedtogether as described will act as a unit, because the successivestresses are not gradually transferred from one slab to the next.

To achieve the desired interaction, the bridge deck slabs must be safelyfixed, both mutually and relative to the base, and for this purpose useis made of the attachment members 16 as shown in FIG. 4 et seq. Theattachment member comprises a metal body having an inclined side 17 withsubstantially the same inclination as the slab side walls, and a lowerside 18 provided with a longitudinal recess 19 spaced from one edge suchthat a remaining rounded ridge 20 is formed at one edge of the inclinedside. The rounded ridge is complementary to the channels 14 and 15,respectively, in the strips 12 and 13, respectively, of the slab 1.Along the opposite edge of the lower side, there is formed a downwardlyextending projection 21. An elongate bore 22 extends transversely of theridge 20 and the projection 21 and through the attachment member body,and a countersunk portion 23 for a screw head is formed in the upperside around the bore. The bridge deck slab is preferably fixed by meansof attachment members 16 only along side.

This being the grooved side in the illustrative embodiment. However, asshown in the drawing, channeled strips (i.e., strips 12 and 13) arearranged at both the tongue and groove sides of the slab. The reason forthis is that in some cases (as, for example) in certain types of bridgeswhere a slab is used instead of an end section), it may be necessary tosecure both sides of a slab. If, in such a case, the attachment positionof the second strip were not provided, special time-consuming measureswould be necessary to secure the corresponding side of the slab.

For connection with the rod surface on land, end sections of the type asshown in FIGS. 2 and 3 are normally used, and they have parts facing thebridge and corresponding to the side portions of the slabs. Each endsection thus comprises a portion provided with a tongue 8' or and groove9', an otherwise inclined side wall and a strip provided with a channel14' or 15'. When an end section with a groove 9' has been fixed inposition, which occurs in that attachment members 16 are positioned suchthat their ridges 20 are fitted in the channel 15', whereupon screws 24are inserted and firmly tightened, the end section is rigidly pressedagainst the underlying structural beams 25. Cylindrical holes 26 of asize adapted exactly to the screw diameter are prebored in the beams.

The first bridge deck slab is then positioned against the beams 25 andis manually inserted as far as possible towards the end section,whereupon the attachment members 16 are mounted in the manner describedabove along the bottom edge which, as seen from the end section,constitutes the farther bottom edge of the deck slabs, and the screws 24are tightened provisionally. Subsequently, a misfit, if any, e.g.because the slab is bent, can be adjusted. Such adjustment may becarried out by driving a thin wedge into the free space between thebottom surface of the attachment member 16 and the beam, between theshank of the screw and the strip 13 of the slab, until the tongue 8 fitsperfectly in the groove 9'. Then the screw joints 24 are completelytightened to prevent any play between the bottom edge of the slab andthe beam. The remaining bridge slabs are mounted and adjusted similarly,until the entire bridge deck is finished and, lastly, the other endsection is mounted. Individual bridge deck slabs can be replaced,without necessitating dismounting of the entire bridge deck up to oneend thereof. Since the tongue and groove have been given the shapeillustrated, with a rounded nose portion of the tongue and roundedtransitions between the groove and adjacent surface portions, the bridgedeck slabs can be raised in the joint area and be easily tilted up andremoved, after the attachment members have been loosened from below.Re-mounting is effected in the reverse order in that the tongue andgroove of the new slabs are fitted in the groove and tongue of theremaining slabs which are held upwardly inclined towards each other andare then pressed down while fitting their tongue and groove. Instead ofthe above-mentioned wedging, other auxiliary means, e.g. hydraulic jacksor the like, can of course be used, which during clamping keep the slabsin engagement with each other by bolting.

The bridge deck according to the invention is, as mentioned above,especially advantageous when used together with a new surfacing whichcan be applied directly to the upper side of the bridge deck slabs. Aportion of such a surfacing is indicated in FIG. 7 and consists of athin layer of primer 27 applied directly to the upper side of thaluminium slabs, a membrane layer 28 of a few millimeters thickness,made of a pressure-distributing and pressure-receiving elastic orelastoplastic material, e.g. two-component acrylic plastic, and uponthis a thicker coating layer or coating-supporting layer 29 of a harderacrylic plastic, preferably provided with embedded mineral grains of awear-resisting material. The drawing shows how the levels 10, 11 closeto the transition between two slabs renders the membrane layer thickerat this point, and thus this layer allows the more rigid layer to yieldwithout breaking up.

One of the advantages of the bridge deck according to the invention isthe low weight which, when the bridge deck is used on existing bridges,affords a pronounced extra load-bearing capacity. Owing to the lowweight, the main supporting structure of new bridges can be made lighterand thus less expensive, which is illustrated by the following example:

A bridge having a span of 50 m and a width of 12 m yields a surface areaof 600 m².

A light concrete slab weighs about 700 kg/m², whereas a deck accordingto the invention weighs about 50-60 kp/m².

It can be roughly estimated that equivalent traffic loads for whichbridges are calculated today are two concentrated loads in the centre ofthe bridge, each weighing 50 Mp, plus steady traffic in two lanes havingan intensity of 0.9 Mp/m².

The maximum bending moment between supports, caused by traffic loads onthe entire bridge will be 1780 Mpm.

The concrete deck yields a moment of 2625 Mpm and the deck according tothe invention 225 Mpm.

In all, the bending moment is thus 4405 Mpm in traditional structuresand 2005 Mpm in a deck according to the invention. The main supportingstructure including the foundation thus need support merely about halfthe load on a deck according to the invention as compared to theconventional design. Thus results, of course, in considerablecost-savings for the expensive main structure.

I claim:
 1. An arrangement in a bridge deck and the like surface-formingstructure to be subjected to mobile concentrated loads moving along saidsurface, said arrangement comprising:a plurality of deck slabs supportedby a base and anchored to said base by corresponding anchoring means,each deck slab including a lower wall, an upper wall extendingsubstantially parallel to said lower wall and of greater side-to-sidedimension than said lower wall such that opposite sides of said upperwall extend outwardly beyond corresponding sides of said lower wall, anda pair of sidewalls joining said opposite sides of said upper wallrespectively to said corresponding sides of said lower wall, one of saidsidewalls having a tongue projecting outwardly from an intermediateportion thereof, the other of said sidewalls having a groove formed inan intermediate portion thereof, said tongue and groove being disposedat slightly different heights of the respective sidewalls relative tosaid lower wall, wherein said deck slabs are arranged side-by-side insuccession, with successive deck slabs being in tongue-in-grooveengagement, and wherein the lower wall of each deck slab has a portionresting on said base at one of the tongue side and the groove side ofthe slab, is held freely space above said base at the other of saidtongue side and said groove side by said tongue-in-groove engagementwith the next slab in succession, and is fixedly anchored to said baseat its resting portion by engagement of the corresponding anchoringmeans with the slab and said base near said one side of the slab.
 2. Anarrangement according to claim 1, wherein each deck slab is anchored tosaid base only at said one side thereof.
 3. An arrangement according toclaim 2, wherein said one side is the groove side of the deck slab. 4.An arrangement according to claim 1, wherein each deck slab furthercomprises a portion projecting outwardly from said lower wall at saidone side of the deck slab, said projecting portion having an upwardlyopen channel formed in an upper side thereof outwardly adjacent to ajunction of said lower wall and the sidewall at said one side of thedeck slab, said projecting portion being anchored to said base by anattachment member of the corresponding anchoring means having anengagement portion engaged within said channel and by bolt means of saidcorresponding anchoring means securing said attachment member to saidbase.
 5. An arrangement according to claim 4, wherein said attachmentmember includes a body portion having an inclined side portion inface-to-face abutment with the sidewall at said one side of the deckslab, said engagement portion of said attachment member being formed ata lower edge of said inclined side portion and being a complementaryshape to said channel, said body portion further having a downwardprojection disposed at an opposite side portion thereof and inengagement with said base, said bolt means extending through a bore insaid body portion.
 6. An arrangement according to claim 5, wherein saidattachment member engages said base only at said downward projection. 7.An arrangement according to claim 1, wherein said tongue has a roundedouter portion and upper and lower sides joined to said outer portion andconverging toward said outer portion from a root portion of said tongue,and wherein said groove is of complementary shape to said tongue.
 8. Anarrangement according to claim 7, wherein said tongue and groove extendsubstantially parallel to said upper and lower walls.
 9. An arrangementaccording to claim 1, wherein said opposite sides of said upper wall arebeveled.
 10. An arrangement according to claim 9, wherein a paving isarranged on upper surfaces of the respective upper walls of said deckslabs, said paving including a thin layer of primer, a membrane layer ofpressure distributing and pressure receiving elastic material on saidprimer layer, and a layer of acrylic plastic on said membrane layer,said layer of acrylic plastic being harder than said membrane layer andhaving mineral grains of wear-resistant material embedded therein, saidmembrane layer being of increased thickness at adjacent beveled edges ofsuccessive deck slabs so as to allow smooth bending of said acrylicplastic layer near the tongue and groove joint between successive deckslabs.
 11. An arrangement according to claim 10, wherein said membranelayer includes a two-component acrylic plastic.
 12. An arrangementaccording to claim 4, wherein said sidewalls have respective portionswhich incline outwardly relative to the corresponding sides of saidlower wall.
 13. An arrangement according to claim 12, wherein saidoutwardly inclined portions join with said lower wall.
 14. Anarrangement according to claim 13, wherein each deck slab furtherincludes inclined brace walls intermediate said sidewalls and joiningsaid upper and lower walls to one another.
 15. An arrangement accordingto claim 14, wherein said brace walls have rounded corners at theirjunctions with said upper and lower walls.
 16. An arrangement accordingto claim 14, wherein said channel is positioned adjacent to a line ofintersection of a center plane of said lower wall, a center plane of theinclined sidewall portion at said one side of the deck slab, and acenter plane of a brace wall.
 17. An arrangement according to claim 16,wherein each deck slab and attachment member are made of light metal.18. An arrangement according to claim 17, wherein said light metal isaluminum.
 19. An arrangement according to claim 6, wherein said bore isnon-circular and shaped to permit adjustment of said attachment memberrelative to said bolt means along said base prior to final tightening ofsaid bolt means.